Shaft driver device and conveyor system embodying the same

ABSTRACT

A shaft driver device is disclosed for use, illustratively, in a roller-type load conveyor or like system in which load units are halted for the performance of an operation thereon, with a consequent increased drag on a normally powered roller of the conveyor which is driven by the device. The system and drive device incorporate means which acts quite independently of any control factor, other than the drag effect, to interrupt the drive of the conveyor roller, or equivalent element in a different installation, immediately upon the arising of drag in excess of a critical value, restoring the drive when that value diminishes or the drag ceases. The drive control means referred to is built in its entirety into the structure of a driven roller or other shaft-driven component comparable thereto. More specifically, the system comprises a first hub member normally rotating with the driver shaft and powered from an appropriate source, a second hub member coaxial with the first member, and means in the form of a torsion spring clutch device normally coupling said members for rotation as a unit under a drag load less than the critical value. The first member is shown as having a resilient driving connection to the second member which, on excess load, yields and causes the torsion spring coupling means to be de-clutched, the shaft drive then coming to a halt. This drive connection is adjustable as to its resilient bias to determine the critical value.

United States Patent [1 1 Cowen, Jr.

[111 3,782,515 Jan. 1,1974

[ SHAFT DRIVER DEVICE AND CONVEYOR SYSTEM EMBODYING THE SAME William E.Cowen, Jr., Westland, Mich.

221 Filed: Sept. 30, 1970 21 Appl. No.: 72,884

Related US. Application Data [62] Division of Ser. No. 698,533, Jan. 17,1968, Pat. No.

[75] Inventor:

[52] US. Cl 192/56 C, 64/30 E [51] Int. Cl. F16d 43/20 [58] Field ofSearch 192/56 C, 41 S; 64/30 E; 81/524 R [5 6] Reierences Cited UNITEDSTATES PATENTS 2,468,193 4/1949 Goff 81/524 R X 1,561,537 11/1925 Hayes192/56 C X 2,626,029 l/1953 Gutterman.... 192/56 C 2,885,873 5/1959Beeston, Jr. 192/84 PM X 3,339,819 9/1967 Gollos .1 192/84 PM X3,636,277 l/1972 Pohlcr 192/84 PM [57] ABSTRACT A shaft driver device isdisclosed for use, illustratively, in a roller-type load conveyor orlike system in which load units are halted for the performance of anoperation thereon, with a consequent increased drag on a normallypowered roller of the conveyor which is driven by the device. The systemand drive device incorporate means which acts quit e independently ofany control factor, other than the drag effect, to interrupt the driveof the conveyor roller, or equivalent element in a differentinstallation, immediately upon the arising of drag in excess of acritical value, restoring the drive when that value diminishes or thedrag ceases. The drive control means referred to is built in itsentirety into the structure of a driven roller or other shaft-drivencomponent comparable thereto.

More specifically, the system comprises a first hub member normallyrotating with the driver shaft and powered from an appropriate source, asecond hub member coaxial with the first member, and means in the formof a torsion spring clutch device normally coupling said members forrotation as a unit under a drag load less than the critical value. Thefirst member is shown as having a resilient driving connection to thesecond member which, on excess load, yields and causes the torsionspring coupling means to be de-clutched, the shaft drive then coming toa halt, This drive connection is adjustable as to its resilient bias todetermine the critical value,

4 Claims, 11. Drawing Figures Ill/I as 42 410 8 J PATENTEDJAN Ham sum 3BF 3 SHAFT DRIVER DEVICE AND CONVEYOR SYSTEM EMBODYING THE SAME This isa division of application Ser. No. 698,533, filed Jan. 17, 1968, nowU.S. Pat. No. 3,605,990.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention hasapplication, in an embodiment herein illustrated and described, in thefield of what is termed live roller conveyors, as distinguished fromgravity type roller conveyors. More particularly, applications inso-called accumulation conveyor systems are presently contemplated.However, the invention in its broadest aspect is applicable to manyother fields in which it is desired to interrupt the drive of arotatively powered shaft in immediate response to the arising of anoverload on said shaft, frictionally occasioned or otherwise. Anapplication in automated transfer equipment is illustrative.

2. Description of the Prior Art In the field of accumulation and relatedtype conveyors I am unaware of any prior art pertaining to a live rollerconveyor system, in which the drive of a roller or rollers is, uponarising of a predetermined rotationresisting load thereon,instantaneously interrupted by means incorporated in effect solely inthe roller structure; i.e., independently of other external meansemployed in known arrangements.

Conveyor systems of the last named sort are the subject matter ofpatents to Burt U.S. Pat. No. 3,122,232 of Feb. 25, 1964, De Good et alU.S. Pat. No. 3,136,406 of June 9, 1964, De Good U.S. Pat. No. 3,156,345of Nov. 10, 1964, and Fix U.S. Pat. No. 3,285,381 of Nov. 15, 1966. Theequipment disclosed in all of these patents employs some sort of loadfeeler means, mechanically or electrically responsive to a halt of aload unit, to transmit a de-clutching action to a live roller of thesystem. That is, the halting of the drive is not solely in response toan increased frictional shaft drag alone, occasioned by the halting.

In specific regard to the releasable torsion spring clutching of apowered rotative input shaft to a rotative output shaft, there are ofcourse many patents relating to spring-type overload release devices forthis purpose. The most pertinent to the structure of the presentinvention appear to be Goff U.S. Pat. No. 2,468,193 of Apr. 26, 1949,and Gutterman U.S. Pat. No. 2,626,029 of Jan. 20, 1953. These relate,however, to simple tool devices, as distinguished from a conveyorsystem. Moreover, in regard to specific structural details, Goff andGutterman fail to disclose the improved combination of resilientlyoperated clutch release feature, particularly where the clutch is itselfa torsion spring type. 1

Such is the subject matter of the more specific claims of the presentapplication.

SUMMARY OF THE INVENTION The invention, as embodied in particular in alive roller conveyor system, features a suitably supported system ofconveyor rollers which support load units from beneath, directly orindirectly, for transport in a longitudinal direction, which load unitsare adapted to be halted from time to time, either automatically ormanually by an operator, for the performance of some operation thereonwhile halted.

Due to the fact that the roller system is responsive without recourse toload sensing means or the like, as indicated above, it is of greatsimplicity, compactness and little cost. Further, in a preferredembodiment its roller provisions and a motorized drive therefor occupy avery small height above the floor; and such provisions are readilyaccessible for maintenance. Being free of external controls, electricalor mechanical, and other than a frictional drag effect, it is possible,when desired or necessary, for the operator or attendant to push a loadunit or units back any desired distance, reversely of the normal traveldirection thereof.

Of great importance is the fact that it is unnecessary, at any time tostart or stop a prime mover of the installation, or to de-clutch itsmain and common driving connection to a number of roller units of thesystem.

The system is capable of handling many different types of loads,palletized or otherwise. While as indicated above, its rollers engageand drive the load units directly from beneath, this function may ifdesired be performed through the agency of a continuous load belt, in aknown manner. However, in the interest of the desired compactness,particularly above-floor, such supplemental belt provisions may beomitted.

Pursuant to the principle of the invention, a simple spring adjustmentadapts the system to handle load units in a wide range of weights, withvarying sensitivity as to drag and with uniformly good efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspectiveview, partially broken away, showing a series of live rollers asincorporated and driven in a typical motorized conveyor system pursuantto the invention;

FIG. 2 is a fragmentary side elevational view adaptation of theinvention in a continuous, horizontal, uniplanar loop system;

FIG. 3 is a view partially broken away and in section through the axisof a torsion spring-clutched and normally powered shaft and roller unitof theinvention, as along line 33 of FIG. 4;

FIG. 4 is an end view of that unit, as from the right of FIG. 3, beingpartially broken away and in transverse vertical section on a linecorresponding to line 4-4 of FIG. 3;

FIG. 5 is a fragmentary view in enlarged scale and in transversevertical section on broken line 5-5 of FIG.

FIG. 6 is an exploded view illustrating components of a typical shaftand roller drive unit which differs in certain aspects from what isshown in FIGS. 1-5;

FIG. 6A is a fragmentary sectional view showing a compositedual-sprocket and hub feature of the unit of FIG. 6;

FIG. 7 is a fragmentary view illustrating a control device in which theload drag-responsive de-clutching of the drive shaft is effected in analternative manner, i.e., through the agency of magnetic means;

FIG. 8 is a schematic view in side elevation illustrating a typicalembodiment of the invention in a straight line conveyor system employingparallel, vertically spaced, load advance and return reaches;

FIG. 9 is a schematic top plan view of another adaptation of theinvention in a continuous, horizontal, uniplanar loop system; and

FIG. 10 is a top plan view of a still further alternative embodiment ina single reach horizontal system.

DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 and 2 show an illustrativeembodiment of the equipment of the invention in a single reach,horizontal live roller-type accumulation conveyor system, of the generaltype depicted in FIG. 10. This conveyor comprises an elongated uprightframe, generally designated lll, typically comprised of corner uprights12 braced by cross pieces 13 and mounting elongated front and rearroller supporting bar members 14 which parallel and are spacedtransversely from one another. Elongated lower frame members 15 aresustained by the uprights 12, the members I5 supporting a horizontalplatform 16 upon which motorized drive means, hereinafter described, arein turn sustained. In a known fashion, the frame members 12, 13, 14 and15 may be constituted by channel sections, or the like; and it is to beunderstood that additional intermediate uprights corresponding to thecorner uprights 12 are contemplated, in a number determined by theoverall length of the system 10.

The front and rear supporting members 14 have means to journal theopposite ends of a number of live conveyor rollers, generally designated18, pursuant to the invention, as well as a suitable number of idlerrollers 19; and the longitudinal spacing between the axes of liverollers 18 is intended to be such that at no time will a load unit befree from the normal driving action of at least one of the rollers 18.Accordingly, the design of any system 10 will essentially and preferablydepend upon the minimum lengthwise dimension (relative to its travelpath) of any load unit, palletized or otherwise, intended to be handledby the system. It is further contemplated that the system 10 shall beequipped with a number of load halting devices, not shown in FIGS. 1 and2 in the interest of simplicity and clarity, but of the nature shown inFIGS. 8, 9 and 10 of the drawings. Lacking such stop means, it isnevertheless contemplated that load units traversing the mechanism 10may be manually halted by the operator or attendant.

As indicated above, the lower platform 16 of the frame 11 supports aspeed reduction gear head 20 which is powered by an appropriately ratedelectric motor 21, through the agency of a motor-driven belt 22 trainedabout an input pulley 23 of reducer 20.

A sprocket 24 is fixed on the output shaft of the reducer; and a maindriving chain 25 of the conveyor mechanism 10 is trained about thebottom of sprocket 24, passing upwards and to the left (FIG. 2) fromsprocket 24 about a tension adjusting idler 26 journaled on an arm 27 ofan appropriate adjusting bracket 28 welded to one of the bottom framechannels 15.

Chain 25 serves as a common drive for the live rollers 18 of the system10, the shaft 30 of each of which is equipped, in the special mannerhereinafter detailed, with a clutch-controlled power input sprocket 31acting as a power-operated driver for the roller in question, from whichsprocket 31 the roller 18 normally receives its drive via adrag-responsive spring clutch means, to be described. In being trainedupwardly and horizontally about the sprockets 31, drive chain 25 ismaintained in efficient drive engagement with those sprockets, forexample by one or more cleats 32 welded to frame support channel 14, thenumber of these downwardly acting, chain restraining devices beingdetermined in accordance with the overall length of the system 10, andthe number of live rollers 18 incorporated therein.

As best illustrated in FIGS. 3, 4 and 5, each of the conveyor rollers 18(shown in dot-dash line in FIG. 3 for simplicity) is powered during thenormal driving phase by a shaft driving and control device pursuant tothe invention, which is generally designated by the reference numeral34. Roller 18 is suitably secured fixedly to the shaft 30, which shaftis a part of the device 34, being shown as journaled in appropriatetransversely aligned and spaced bearing blocks or trunnions 35, boltedon and depending from the top frame members 14. A shaft retainer collar37 is secured to shaft 30 directly outboard of the trunnion 35.

To the right of the other trunnion 36 (FIG. 3) the shaft 30 is reducedin diameter at 38; and reduced portion 38 is surrounded by successivetubular inner and outer bushings 39, 40, with a spacing washer 41interposed between bushing 39 and the adjacent side of trunnion 36. Theinboard bushing 39 serves as a bearing for the chain sprocket 3i, whichhas an integral, axially extending first control hub member 42 ofsubstan tial length, both for added stability and to afford acylindrical outer clutch surface 43., the purpose of which ishereinafter described.

The outer bushing similarly journals an axially elongated second controlhub member 45 having an external cylindrical clutch surface 46; and theclutch surface 43 of the hub member 42 on sprocket 31 and the surface 46are encircled by the coils of a yieldable and resiliently operatingreleasable torsion clutch or coupling spring 47. One end coil of thisspring lies adjacent an enlarged end flange 48 of hub 45, to which it isanchored, as by an axially offset lug 49 (FIG. 4), to the hub. Theopposite end of coiled torsion spring 47 is offset a substantialdistance radially outwardly at an extension control finger 50 (FIG. 3),being engaged at this radially extending member in the de-clutchingoperation of the shaft drive control device 34, in a manner hereinafterdescribed. In the normal, sprocket driven action of that device, clutchspring 47 constrictively engages the clutch surfaces 43, 46 of therespective hub members 42, 45, with the result that the two are coupledfor rotation as a unit under the drive transmitted by chain 25 tosprocket 31.

I-Iub member 45, as thus drivingly connected to the power source,normally transmits driving torque to shaft 30 through the agency of aresiliently acting coupling unit, generally designated 52, the nature ofwhich is illustrated in FIGS. 3, 4 and 5, and which in response to apredetermined increase in frictional drag and yield of the couplingspring 47, de-couples hub members 42, 45 from one another for a relativerotative shift. Typically, unit 52 may comprise a plunger or tappet pin53 slidable in a tubular guide sleeve 54 (FIG. 5), which sleeve extendsinto a recess 55 milled or otherwise formed in the enlarged flange 48 ofhub 45. Sleeve 54 is received between opposite, circumferentiallylimiting sides of recess 55, in a manner to be able to transmit normaldriving torque directly from hub 45 by means of pin 53, i.e., fromsprocket hub 42 through the constricted torsion spring 47, a side wallof recess 55 of hub 45 and the sleeve 54, thus driving the roller shaft30 through a collar connection of that shaft, to be described. A roundedend 53' of pin 53 engages against a flat radially extending surface 57of recess 55, which surface, as appears in FIG. 4, is radially offseteccentrically from, but in radial alignment with, the axis of shaft 30.A coil compression spring 58 in sleeve 54 acts radially outwardly on pinor plunger 53; and the important function of spring 5% will behereinafter described. it is backed radially outwardly by an adjustingset screw 59 (FIG. 5), which screw is threadedly received at the outerend of the pin guide sleeve 541.

The control device Ed is completed by an annular torque-transmittingcollar 6d surrounding the outer end of the reduced diameter portion 38of the drive shaft 3d, the driving connection being effected in anyappropriate way, as by a key 61. Collar 640 has an integral flange 62axially inwardly overlapping and radially spaced from the enlargedflange dd of hub 45; and the outer end of the sleeve 54 which guides pin53 is threaded received in the flange 62. Sleeve 54 is received in hubrecess 55 with pin 53 bearing against sur face 57 of the recess so thatthe sleeve, as rigidly coupled to collar 60) in the latters flange 62,and the spring-backed pin 53 constitute a torque-transmitting couplingbetween the collar and the outer hub 45 of device 34 in the normaldriving phase of the latter.

That is, with the end 53' of pin 53 abutting the radially offset flatsurface 57, of hub d5 i.e., eccentric of the axis of drive shaft 3d,torque is normally transmitted to shaft 30 and roller 18, under africtional drag load on shaft Sill below a predetermined critical value,from the motor and chain driven sprocket Elli and hubs 42, 45 (throughthe agency of the torsion spring 47 encircling the hub clutch surfaces43, 4-6), thence through the pin 53 and the spring guide sleeve 54,collar 60 and key connection M, as shown in FIG. 5. However, when thecritical drag torque value is exceeded, pin 53 is depressed against thebias of its coil spring 58 so that hubs 42 and d5 rotate slightlyrelative to collar 60, with the result that the driving connectionthrough torsion clutch spring d7 is instantaneously interrupted, in amanner and by means now to be described.

To this end, the torque transmitting collar 60 is provided with achordal flat surface 6d (lFlG. d); and an ax ially extending clutchcontrol arm or element 65 of substantial length is secured at one end tothe collar at the flat 6d, as by a lapped connection and locking screw66. As shown in Fifi. 3, the control arm 65 extends axially pastthe'offset finger 5d of the torsion spring 47, being normally spaced atrifle, as indicated at a in FIG. d, from that arm. The spacing is onthe side of spring arm 50 forwardly of the direction of its normalclockwise rotation, indicated by the arrow in FIG. 4; and as operated bythe first control members torsion spring connection, the arms 65 and 50interrupt the driving connection of the driver 31 and second control hubmember d5.

Accordingly, it is seen that, upon depression of pin 53 under a shaftload in excess of the critical value, the spring finger 50 contactscontrol arm 65 of collar 60 in a clockwise direction as viewed in Fit].4 with the result that torsion spring 47 is unwound ever so slightly inreference to the hub clutch surfaces 43, 46. The unwind or expansion isnevertheless sufficient to interrupt the driving connection between hubmembers 42 and 45 (FIG. 3). in consequence, hub member 45 isinstantaneously de-clutched from drive by the sprocket 31, whichcontinues to idle on the bushing 39 without interruption of its owndrive by the chain 25. Shaft 31 and roller ldare tie-clutched to haltthe latter beneath the load; and drive is resumed just as soon as thedrag load on the roller and shaft drops below the critical value,usually upon freeing the load unit for continued advance on the systemor mechanism lid.

The drag torque may be great or small, depending upon the load, i.e.,from a value capable of being overcome by a finger grip on roller id, upto a value far in excess of that. Any setting in such a range, at whichthe pin 53 will yield, with instantaneously decoupling, may be made by asimple manipulation of set screw 59 (FlG. 5) to vary the compression ofspring 5%. This can be done in a system incorporating many live rollers18 in a minimum of down time.

FIG. 6 of the drawings is an exploded view showing in a general way thecomponents of a control device 34', substantially the same as the device43, which has been described above, in the main utilizing the samereference numerals. However, H6. 6 differs from what is shown in FllG.3, in that a compound dual sprocket and hub arrangement is illustrated.

Thus, the sprocket hub member, specially designated 42', is formedintegrally on a barrel-like, hollow cylindrical body 67 which has anintegral and radially enlarged flange 68 apertured to receive a numberof bolts 69. There are two like sprocket members 7% and 71 spacedaxially by a ring member '72; and the members 70, 71 and 72 have holescorresponding in number and spacing to those of flange 6% to receive thebolts 69 the holes of sprocket member 71 being tapped for this purpose.

As depicted in FIG. 6a, the assembly of hub member, sprockets and spaceris rotatably mounted on shaft 30, with bushings 73 interposed. Thefunctioning of the device 34' involves other components such as areshown in H68. 3, t and 5. The dual sprocket arrangement of FIGS. 6 and6a affords a desirable degree of standard ization in respect to theability of hub-carrying member 67 to receive sprockets of differentdesign.

As appears from the foregoing, the concept of drive shaft and rollercontrol clutch means, illustratively in a live roller conveyor system,is considered to be perhaps the most important aspect of the presentinvention, not limited in particular in regard to the specific nature ofthe drag-controlled clutch means interposed between the shaft and aprime mover. FIG. 7 illustrates schematically a very simple arrangementfor the prupose, utilizing a magnetic field for the coupling means.

Thus, a driving disk 7d of substantial mass may be keyed or otherwisedrivingly connected to a reduced diameter end portion 75 of the drivenshaft 76, the latter being journaled in a frame-supported bearing blockor trunnion 77. The sprocket 78 is mounted on shaft member 75 for freerotation thereon, as by a bushing 79.

Pursuant to the embodiment of H6. '7 the sprocket 78, at least at itshub portion 80, and the driver disk 74 present facing surfaces at 81 and82, respectively, which are permanently magnetized, or may each have aseries of magnets embedded therein. The respective magnetic surfacemeans are polarized north and south, and disk 74 and sprocket 78 arerestrained against axial movement relative to shaft 76 or one another.Accordingly, upon the chain drive of sprocket 78 (or any othercorresponding type of drive means), the magnetic field existing betweenthe magnetized portions occasions a drive of the shaft-connected disk74, with consequent rotation of shaft 76 and the load roller or othermeans 83 connected thereto.

The degree of magnetization of the members 74 and 78 of coursedetermines the strength of the field, hence the critical value at whichthe field yields, under restrictive shaft drag, to de-couple theshaft-keyed disk 74 from driver '78. Adjustment of the critical value isreadily effected by replacing the drive disk 74 with another of greateror lesser effective magnetization, in relation to that of driver '78. Itis also contemplated that the disk member 74 might beelectromagnetically energized, with the possibility of effecting adesired adjustment of the magnetic coupling field by varying theelectrical input from an appropriate source.

F165. 8, 9 and 10 depict three types of possible roller conveyor systemsin which the roller drive de-coupling arrangement of the invention maybe employed. FIG. 8 shows schematically an installation 85 in a straightline, floating palletized system having vertically spaced and parallel,rectilinear lower and upper reaches 86, 87, respectively, the latter ofwhich is equipped with longitudinally spaced stop devices 88, manuallyor automatically operated, at certain stations. it is to be understoodthat, although not appearing in FIG. 8, each such station incorporates aseries of the roller and roller control devices 34, which are in suchlongitudinal spacing from one another that no load unit is ever out ofengagement with at least one such device.

Typically, the stations might be a first assembly station 89, a secondassembly station 90, at both of which an assembly operation isperformed, with an accumulation of palletized load units 91 halted bythe respective stop devices 88. Another stop device 92 is shown adjacentthe right hand end of upper reach 87, behind which load units 91accumulate, as in temporary storage, prior to proceeding to a pickupstation at 94, where the loads are removed from their respective pallets95.

The latter are then lowered to the level of bottom conveyor reach 86 bymeans of suitable elevator-type means (not shown), whereupon a pushforwards the same onto the first or right hand (F IG. 8) set of liveroller devices 34.. Like reach 87, the reach 86 has a number of suchsets, along which the empty pallets are transported to the left,accumulating behind a rear stop member 97 at what may be considered apallet storage station 98.

Upon release of stop 97, the pallets travel onto rollers at a partloading and elevator station 99, where load units 911 are placed on thepallets, the load and pallet then being elevated, by means not shown, tothe level of upper reach 87. A push to the right places the load unitson a starting station at 100, upon which their travel proceeds to theright in the manner and for the purposes mentioned above.

FIG. 9 shows a typical installation 1102 in a closed loop system, forexample a foundry mold line. Considering station 103 as being a startstation, at which the mold drag is placed on the rollers 18, the partsproceed to the right to an accumulated stop at station 104 behind a stopdevice 105, where the molding cores may be set in place in the drag,thence to a station 106, behind another stop, at which the mold cope isapplied. Further stations at 107 may represent a weight setting or moldclumping station and a pouring station 108, each behind manually orautomatically operated stops 105.

The poured molds then proceed, always under the drive of devices 34,about the right hand loop of the system 102, accumulating behind a stopat a weight pick-off or unclamping station 110, then proceeding uponrelease of the stop to a cope pick-off station 111. The cycle iscompleted by powered travel of the load units around the left-hand bightof the loop, coming to rest at a drag pick-off station 112. The cyclerepeats in the manner described above.

FIG. 10, on the other hand, schematically shows an installation 114 in astraight line, floating system, the start of conveyance of which is at aright-hand station 115. The load units proceed to accumulate behind afirst automatic or manual stop 116, where or after which a machiningoperation may be performed. Following release, accumulation next takesplace behind a metering stop 1 17, prior to proceeding to an assemblystation, as at 118. Assembled parts then travel, roller driven asbefore, to accumulation in a final station 119 behind an end stop 120,where they may remain stored for a later operation, or if somesucceeding part of the system is temporarily shut down.

Accordingly, it is seen that the invention, systemwise, has greatversatility. It is also inherently compact and of low production cost,due to the improved nature of the individual devices 34, free fromreliance on external control means and lack of need for belt powertransmission. As indicated above, the power source or prime mover of anyinstallation embodying a considerable number of the live rollers mayoperate uninterruptedly to continue the drive of all such rollers as arenot halted. The power input sprocket of the halted roller simply idlesabout the shaft of the latter. It is of course contemplated that theremay be other input members equivalent to the sprocket, such as a gear, apulley, or the like.

As also indicated above, the principle of the invention has wideapplication in industry, over and above purely live roller types ofaccumulation conveyor systems, such as are illustrated in FIGS. 8, 9 and110. For example, an application is contemplated in automated machinetool transfer equipment, in which systems of the type depicted in FIGS.1 and 2 would extend, parallel to one another, between opposite parallellines of machine tools past which workpieces are indexed stepby-step.The live roller units would effect the transportation at a desired rateof the workpieces, palletized or not, between opposite ends of theproduction lines, permitting loading of pallets, unloading or any othertype of supply or maintenance function. An installation such as thatreferred to would replace known types of so-called power and freeequipment which has been used for the purpose, with halted load unitsnot subject to scufi'ing from beneath by continuously driven loadrollers. Other installations will suggest themselves to those skilled inthe art.

What is claimed is:

1. A control device to govern the drive of a rotative shaft subject to avariable drag under load, said device acting responsively to an increasein said drag about a predetermined value, and comprising means toreleasably connect the shaft to a driver therefor in a manner toautomatically interrupt the shaft drive solely in response to saidincrease in drag, said means comprising a first hub member surroundingsaid shaft and normally rotating with the shaft and driver, a second hubmcm' ber surrounding said shaft coaxial with and coacting with saidfirst member, and yieldable torsion spring means normally engaging andfrictionally coupling said first and second members for rotation as aunit, said coupling means and one of said first and second membershaving means responsive to said predetermined increase in drag and aconsequent yield of the coupling means to operatively de-couple thefirst and second hub members from one another.

2. A control device to govern the drive of a rotative power drivenmember subject to a variable drag under load, said device actingresponsively to an increase in said drag above a predetermined value andcomprising means to releasably connect said member to a driver thereforin a manner to automatically interrupt the drive of said member solelyin response to said increase in drag, said means comprising a secondcontrol hub member normally rotating coaxially with said driven memberand responsive to said drag increase, a first rotatable control hubmember coaxial with said second control hub member and coupled togetherby yieldable torsion spring coupling means, resiliently acting meansnormally coupling said second and driven members for rotation as a unit,said second and driven members being rotatively shifted coaxiallyrelative to one another in opposition to said resiliently acting meansin response to said predetermined increase in drag, accompanied a yieldof the torsion spring coupling means, said torsion spring coupling meansrotating coaxially with said first and second members and includingmeans actuated in response to said relative rotative shift tooperatively disconnect said first and second control hub members fromone another and thereby interrupt the rotative drive of said drivenmember.

3. A self-contained shaft drive control device, comprising a rotatableshaft, a power-operated driver coaxial with said shaft, and releasableclutch means coaxially rotatable with said shaft and driver in a normal,power-driven operation of the shaft, said driver being mounted forrotation relative to the shaft upon release of said clutch means, saidclutch means comprising a second control member coaxial with said shaft,resiliently acting means normally coupling said control member with saidshaft for an impositive drive of the latter through said second controlmember, a first control member coaxially mounted on said shaft forrotation therewith or relative thereto and fixed to said driverresiliently acting means yielding in response to a resistance torotation of said shaft in excess of a predetermined value, said membersrotating relative to said shaft upon said yielding, a torsion springnormally acting to drivingly couple said control members for rotation asa unit, and means operated by said second control member and engagingsaid torsion spring upon said relative rotation of the second controlmember and shaft to interrupt the driving coupling of the first andsecond control member by said torsion spring.

4. The device of claim 3, in which said second control member comprisesa hub encircling said shaft in endto-end relation to said first controlmember, said tor sion spring normally acting on said hub and a coaxialhub of the driver which constitutes said second control member, thesecond control member being provided with an element engageable with anend of said torsion spring upon said relative rotation of said secondcontrol member and shaft, the opposite end of said torsion spring beinganchored by said second control member.

1. A control device to govern the drive of a rotative shaft subject to avariable drag under load, said device acting responsively to an increasein said drag about a predetermined value, and comprising means toreleasably connect the shaft to a driver therefor in a manner toautomatically interrupt the shaft drive solely in response to saidincrease in drag, said means comprising a first hub member surroundingsaid shaft and normally rotating with the shaft and driver, a second hubmember surrounding said shaft coaxial with and coacting with said firstmember, and yieldable torsion spring means normally engaging andfrictionally coupling said first and second members for rotation as aunit, said coupling means and one of said first and second membershaving means responsive to said predetermined increase in drag and aconsequent yield of the coupling means to operatively de-couple thefirst and second hub members from one another.
 2. A control device togovern the drive of a rotative power driven member subject to a variabledrag under load, said device acting responsively to an increase in saiddrag above a predetermined value and comprising means to releasablyconnect said member to a driver therefor in a manner to automaticallyinterrupt the drive of said member solely in response to said increasein drag, said means comprising a second control hub member normallyrotating coaxially with said driven member and responsive to said dragincrease, a first rotatable control hub member coaxial with said secondcontrol hub member and coupled together by yieldable torsion springcoupling means, resiliently acting means normally coupling said secondand driven members for rotation as a unit, said second and drivenmembers being rotatively shifted coaxially relative to one another inopposition to said resiliently acting means in response to saidpredetermined increase in drag, accompanied by a yield of the torsionspring coupling means, said torsion spring coupling means rotatingcoaxially with said first and second members and including meansactuated in response to said relative rotative shift to operativelydisconnect said first and second control hub members from one anotherand thereby interrupt the rotative drive of said driven member.
 3. Aself-contained shaft drive control device, comprising a rotatable shaft,a power-operated driver coaxial with said shaft, and releasable clutchmeans coaxially rotatable with said shaft and driver in a normal,power-driven operation of the shaft, said driver being mounted forrotation relative to the shaft upon release of said clutch means, saidclutch means comprising a second control member coaxial with said shaft,resiliently acting means normally coupling said control member with saidshaft for an impositive drive of the latter through said second conTrolmember, a first control member coaxially mounted on said shaft forrotation therewith or relative thereto and fixed to said driverresiliently acting means yielding in response to a resistance torotation of said shaft in excess of a predetermined value, said membersrotating relative to said shaft upon said yielding, a torsion springnormally acting to drivingly couple said control members for rotation asa unit, and means operated by said second control member and engagingsaid torsion spring upon said relative rotation of the second controlmember and shaft to interrupt the driving coupling of the first andsecond control member by said torsion spring.
 4. The device of claim 3,in which said second control member comprises a hub encircling saidshaft in end-to-end relation to said first control member, said torsionspring normally acting on said hub and a coaxial hub of the driver whichconstitutes said second control member, the second control member beingprovided with an element engageable with an end of said torsion springupon said relative rotation of said second control member and shaft, theopposite end of said torsion spring being anchored by said secondcontrol member.